The invention relates to polyester compositions, methods to synthesize the compositions and articles made from the compositions.
Polycarbonate (PC) is a useful engineering plastic for parts requiring clarity, high toughness, and, in some cases, good heat resistance. However, polycarbonate also has some important deficiencies, among them poor chemical and stress crack resistance, poor resistance to sterilization by gamma radiation. Polycarbonates may be blended with other different, miscible or immiscible polymers, to improve various mechanical or other properties of the polycarbonate. For applications requiring improved mechanical properties, miscible blends are useful, as they also allow use of the blends for applications requiring transparency. Specifically, polyesters may be blended with polycarbonates for improved properties over those based upon either of the single resins alone. However, other properties of polycarbonates, specifically optical properties, may be adversely affected by forming a blend, where the polycarbonate can form a hazy appearance and diminished light transmittance.
The compound, 1,1-bis(4′-hydroxy-3′-methylphenyl) cyclohexane (hereinafter also referred to as DMBPC) has been used as an aromatic dihydroxy compound monomer or comonomer for preparing polycarbonates, which are generally characterized with high glass transition temperatures. For example, polycarbonate homopolymers have been prepared by an interfacial polycondensation method using phosgene and monomers such as DMBPC. Polycarbonates derived from DMBPC can be used in making optical data storage products. DMBPC is generally prepared by reacting cyclohexanone with o-cresol in the presence of a condensation catalyst. However polycarbonates derived from DMBPC, suffer from such as increased brittleness and discoloration in the polycarbonates, thereby affecting the transparency of polymer.
Transparent, miscible compositions of any two polymers are rare. The term “miscible,” as used in the specification, refers to compositions that are a mixture on a molecular level wherein intimate polymer-polymer interaction is achieved. Miscible compositions are transparent, not opaque. In addition, differential scanning calorimetry testing detects only a single glass transition temperature (Tg) for miscible blends composed of two or more components. Thus miscibility of polycarbonate with the polyesters gives the blends the clarity needed.
Clear polycarbonate/polyester blends have been reported in U.S. Pat. Nos. 4,619,976; 4,188,314; 4,391,954; 4,188,314; 4,125,572; 4,391,954; 4,786,692; 4,897,453; 5,478,896; 4,125,572; 4,786,692 and 4,645,802 and GB patent 1,121,866 disclose clear blends based on bisphenol A polycarbonate with a variety of polyesters for example poly(1,4-tetramethylene terephthalate), poly(1,4-cyclohexylenedimethylene terephthalate) and selected copolyesters and copoly(ester-imides) of poly(1,4-cyclohexylenedimethylene terephthalate). However, the heat resistance and impact strength of bisphenol A polycarbonate blends based on these compositions is reduced significantly relative to polycarbonate alone. The application US20020115792 discloses translucent compositions including an aromatic polycarbonate, a cycloaliphatic polyester and a polyolefin having low temperature impact strength. Blends of polyesters with polycarbonate having special cyclic bridging group is disclosed in U.S. Pat. Nos. 5,104,723; 5,132,154 and EP patent 0 683208A2 and EP 02 724172A2.
There exists an unmet need to provide an article with a good balance of optical property, improved heat resistance, processability, and mechanical properties and flame resistance.
For the foregoing reasons, there is an unmet need to develop methods for making polyester blend compositions that can provide a combination of high heat, good optical properties without loss in the mechanical properties.
For the foregoing reasons, there is an unmet need to develop articles derived from such blend compositions that can provide a combination of high heat, good optical properties without loss in the mechanical properties.
For the foregoing reasons, the industry needs to develop technologies that can provide molding compositions having useful mechanical and optical properties with polyesters having high heat resistance and good optical properties.